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AngularJS Directive Tutorial with Examples

  1. What is Directive?
  2. Directive with templateUrl

1. What is Directive?

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What is the Directive in AngularJS? There are many answers to this question that you can find on Google. But it's too lengthy, and I like a shorter answer.
  • Directive is an instruction for you to create a "TheNew". "TheNew" herein can be a new tag or create a new attibute for a tag, or a new CSS tag, or a Comment .
  • And Directive shows AngularJS how to convert "The New" into HTML code that the browser can understand.
Example, I create a Directive called "helloWorld" to define a new <hello-world> tag, and I use this tag in HTML file. A browser obviously does not understand this tag, but when the file is run in the browser, AngularJS will rely on the above Directive instructions to convert the <hello-world> tag into HTML that the browser can understand.
Directive E (Element):
Nothing is better than starting with an example. How can I create a new tag?
On any folder you create 2 directive-e-example.html & directive-e-example.js files:
directive-e-example.js
// Create an Application named "myApp"
var app = angular.module("myApp", []);

// Create a Directvie named "helloWorld"
app.directive("helloWorld", function() {
    return {
        restrict : "E",
        template : "<h1>Hello World!</h1>"
    };
});
In the above Javascript , firstly, create a module (app), then create a Directive named helloWorld for this module . The name of a Directive has to be in accordance with the camelCase rules.
  • Các cách đặt tên trong các ngôn ngữ lập trình
directive-e-example.html
<!DOCTYPE html>
<html>
   <head>
      <title>AngularJS Directive</title>
      <!-- Check version: https://code.angularjs.org/ -->
      <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.7.2/angular.min.js"></script>
      <script src="directive-e-example.js"></script>
   </head>
   <body>
      <div ng-app="myApp" ng-controller="myCtrl">
         <h3>Directive E (Element):</h3>

         <hello-world></hello-world>

      </div>
   </body>
</html>
Open the directive-e-example.html file on browser, and you have the following result:
Directive A (Attribute)
In this example, I will create an attribute named good-bye for a tag of HTML:
We will create 2 directive-a-example.html & directive-a-example.js files:
directive-a-example.js
// Create an Application named "myApp"
var app = angular.module("myApp", []);

// Create a Directvie named "helloWorld"
app.directive("goodBye", function() {
    return {
        restrict : "A",
        template : "<h1>Good Bye!</h1>"
    };
});
directvie-a-example.html
<!DOCTYPE html>
<html>
   <head>
      <title>AngularJS Directive</title>
      <!-- Check version: https://code.angularjs.org/ -->
      <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.7.2/angular.min.js"></script>
      <script src="directive-a-example.js"></script>
   </head>
   <body>
      <div ng-app="myApp" ng-controller="myCtrl">
         <h3>Directive A (Attribute):</h3>

         <div good-bye></div>

      </div>
   </body>
</html>
Open the directive-a-example.html file on browser and receive the result:
Directive C (Class)
directive-c-example.js
// Create an Application named "myApp"
var app = angular.module("myApp", []);

// Create a Directvie named "errMessage"
app.directive("errMessage", function() {
    return {
        restrict : "C",
        template : "<h1>Something Error!</h1>"
    };
});
directive-c-example.html
<!DOCTYPE html>
<html>
   <head>
     <title>AngularJS Directive</title>
      <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.7.2/angular.min.js"></script>
      <script src="directive-c-example.js"></script>
   </head>
   <body>
      <div ng-app="myApp" ng-controller="myCtrl">
         <h3>Directive C (Class):</h3>

        <div class="err-message"></div>

      </div>
   </body>
</html>
Directive M (Comment)
directive-m-example.js
// Create an Application named "myApp"
var app = angular.module("myApp", []);

// Create a Directvie named "myComment"
app.directive("myComment", function() {
    return {
        restrict : "M",
        replace : true,
        template : "<h1>OK Important!</h1>"
    };
});
directive-m-example.html
<!DOCTYPE html>
<html>
   <head>
     <title>AngularJS Directive</title>
      <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.7.2/angular.min.js"></script>

      <script src="directive-m-example.js"></script>
   </head>
   <body>
      <div ng-app="myApp" ng-controller="myCtrl">
         <h3>Directive M (Comment):</h3>

        <!-- directive: my-comment -->

      </div>
   </body>
</html>

2. Directive with templateUrl

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Normally, when you create a Directive you have to provide a HTML content through the "template" property. If the HTML content is too long, it will be a problem. In this case, you should put this HTML content into a file, and then use the "templateUrl" property to point to the position of such file .
In this example, I have a data which is tasks to be done and I will create a Directive named "myTodoList". The data will be displayed like the following illustration:
todo-template.html
<div class="my-todo-list">
  <h1>{{title}}</h1>

  <div ng-repeat="todo in todoList">
    <input type="checkbox" ng-model="todo.completed"> {{todo.name}}
  </div>

</div>
todo-example.js
var app = angular.module("myApp", []);

var ctrl = app.controller("myCtrl", function($scope) {

  $scope.todoDatas = [
    {name: 'Create a custom directive', completed: true},
    {name: 'Learn about restrict', completed: true},
    {name: 'Master scopes', completed: false}
  ];

});

// Create a Directive named "myTodoList"
// E: Element <my-todo-list todo-list="=" title="@">
app.directive("myTodoList", function() {
    return {
        restrict : "E",
        templateUrl : "todo-template.html",
        // '=' : an expression
        // '@': a string
        scope: {
          todoList: '=',
          title: '@'
        }
    };
});
todo-example.html
<!DOCTYPE html>
<html>
   <head>
      <title>AngularJS Directive</title>
      <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.7.2/angular.min.js"></script>
      <script src="todo-example.js"></script>
      <style>
         .my-todo-list  {
           border: 1px solid #ddd;
           padding: 5px;
           margin: 5px;
           width: 320px;
         }
      </style>
   </head>
   <body>
      <div ng-app="myApp">
         <div  ng-controller="myCtrl">
            <h2>Custom Directive with templateUrl</h2>

            <!-- $scope.todoDatas -->
            <my-todo-list todo-list="todoDatas" title="My Todo List"/>

         </div>
      </div>
   </body>
</html>
You need to run the todo-example.html file on a HTTP Server, which is mandatorybecause templateUrl requires that data source must be from http or https. It doesn't accept data source, coming from file:///.
OK, I will explain the code of the above example
The above illustration shows that we are creating a Directive named "myTodoList". It's like you create a new <my-todo-list> tag with two todo-list & title attributes.
  • '@' implies that it is a String.
  • '=' implies that it is an Expression.
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